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Ktt€osteUo: Magnetism 1
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1.1 Compare and Contrast
a Magnetic Field
Electrostatic vs. Magnetic Interactions (Sec 36.1)
Fill in the table that follows to indicate how magnetic poles are different from or the same as positively
or negatively charged objects.
The north pole ofabar magnet
always attracts the south pole of
another bar magnet and repels
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other bar’s north pole.
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pole nor the south
Neither the
poleofamagnetexertsaforceona
small aluminum ball hanging at the
end of a thin, non-conducting thread.
north
n,
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A foam tube is charged by rubbing
so that one end is positive and the OJt’
other negative. You find that both
ends attract the north pole of a bar
magnet (and the south pole)
is
Lt
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r
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is positively charged on one
end and negatively charged on the end into half, one rod
will stay positively charged, the other rod wIll stay
negatively charged.
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When you cut a rod that
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Electrostatic Interaction
Magnetic Interaction
What property of objects
determine whether they
participate in the interaction?
What is the direction of the
force between the interacting
objects?
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Isolation of properties
(+) charges and (-) charges
cannot be isolated.
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North pole and south pole can
cannOt be isolated.
1
stello: Magnetism 1
12 Observe and Sketch
Draw the following in the appropriate space provided.
a Pattern of iron filings with bar magnet
b. Pattern of compasses surrounding bar
magnet
c. Pattern of iron filings: North vs. South pole
d. Pattern of iron filings: South vs. South pole
e. Find a pattern: Where do the lines” start? Where do they end? How do you know?
f.
Are there any similarities or differences between the lines created by iron filings vs. the
direction of the compasses?
2
osteflo: Magnetism 1
g.
A horseshoe magnet is simply a bar magnet that has been
bent so that the north and south poles are near each other.
Make a sketch of how the iron filing pattern might look.
V
—
-
—--
—
Magnetic field lines: A magnetic field can be represented with magnetic field lines. They have the
following properties (Sec 36.2):
• The direction of the magnetIc field line at a point is the same direction as the magnetic field at
that point
and end on
• The magnetic field lines start on
i,V.
Th
• The magnitude of the field at a point is represented by the density or concentration of the lines
near that point.
• The number of lines leaving or terminating on a charged object is proportional to the magnitude
of its pole.
• Magnetic field lines NEVER cross.
• Magnetic field lines are strongest
3
astello: Magnetism 1
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1.3 Sketch Draw the appropriate magnetic field lines for the following diagram (Sec 36.2 and 365):
b. North pole north pole
a. Horseshoe magnet
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N
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d. South pole south pole
c. South pole north pole
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f. Current-carrying wire
e. Current-carrying wire
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1o: Magnetism 1
1.4 How are magnetic fields produced? (Sec. 36.3)
a) Produced by I
t[
(the motion of electric
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charge)
b) Electrons In the atom are in constant motion. The two kinds of electron motion are:
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Lt
The main contributor to magnetism is t
most common magnets.
c) Every spinning electron is a tiny magnet
in
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• A pair of electrons spinning in the same direction:
• A pair of electrons spinning in opposite directions: 1’
d) In materials such as iron, cobalt and nickel, the fields
1.5 Magnetic Domains (Sect. 36.4)
a) Magnetic domains: clusters of magnetically aligned atoms
b) For the iron to be magnetic, the magnetic
domain must be
c) Why are most objects not magnetic?
d) How are permanent magnets made?
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(b
FIG. 627. Magnetic domains h a ierromagnetic solid. (a) flan.
dom damains when unmagnetized. (b) Parailet alignment of do
mains as a result of an external magnetic field.
e) Why do magnets get weaker when dropped or heated?
Homewotk: Read Sections 36.6-36.9. Answer Check Concepts Questions (pg 735 and 736)
11-20.
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